Preparation method and application of solid adsorbent

Abstract

The application belongs to the technical field of solid adsorbent composition, and discloses a preparation method and application of a solid adsorbent. The method comprises the following steps: weighing and mixing at least one siliceous porous base material and calcium silicate aluminate-containing solid waste incineration residue according to a preset ratio to obtain a first mixed material; adding a binder and a surfactant to the first mixed material, and mixing to obtain a second mixed material; providing a leaching solution, wherein the leaching solution is obtained by mixing and leaching the calcium silicate aluminate-containing solid waste incineration residue and deionized water; adding a solidifying agent and the leaching solution to the second mixed material, and mixing to obtain a to-be-processed mixture; and soaking the to-be-processed mixture, and then performing post-processing to obtain the solid adsorbent. By using the solid waste incineration residue leaching solution as a modification aid of the solid adsorbent, the application realizes the synergistic improvement of low-cost preparation and high-efficiency phosphorus removal performance.

Description

Technical Field

[0001] This invention belongs to the technical field of solid adsorbent compositions, specifically relating to a method for preparing a solid adsorbent and its application. Background Technology

[0002] Phosphorus is a core pollutant in eutrophication and a non-renewable strategic resource. Excessive phosphorus discharge leads to rampant algal blooms, causing ecological disasters such as algal blooms and red tides, disrupting the ecological balance of aquatic bodies, and threatening drinking water safety and the development of the aquaculture industry. Furthermore, with global population growth and accelerated industrialization, phosphate rock resources are becoming increasingly depleted, and phosphorus shortage has become a significant bottleneck restricting the sustainable development of agriculture and industry. Therefore, the efficient recovery of phosphorus from phosphorus-containing wastewater to achieve the dual goals of "phosphorus removal" and "phosphorus recovery," possessing significant environmental governance value and resource recovery significance, is currently a research hotspot and key direction in the field of environmental engineering.

[0003] Numerous studies have shown that metal elements such as Ca, Fe, Al, and Cu in some solid waste incineration residues are the core active sites for phosphorus adsorption, and the content and form of metal ions are positively correlated with the phosphorus adsorption capacity of solid waste incineration residues. However, unmodified solid waste incineration residues suffer from defects such as insufficient exposure of metal active sites, loose surface pore structure, and small specific surface area, resulting in low phosphorus adsorption capacity and poor adsorption selectivity, making it difficult to meet the treatment requirements of phosphorus-containing wastewater. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for preparing and applying a solid adsorbent. By using leachate from solid waste incineration residue as a modifying agent for the solid adsorbent, a synergistic improvement in low-cost preparation and high-efficiency phosphorus removal performance is achieved.

[0005] The objective of this invention is achieved through the following technical solution: This invention provides a method for preparing a solid adsorbent, comprising the following steps: At least one siliceous porous matrix material and calcium aluminosilicate solid waste incineration residue are weighed and mixed according to a preset ratio to obtain a first mixture. A binder and a surfactant are added to the first mixture, and the mixture is then mixed to obtain a second mixture. A leachate is provided, which is obtained by mixing and leaching the calcium aluminosilicate-containing solid waste incineration residue with deionized water; in the process of obtaining the leachate, the solid-liquid ratio of the calcium aluminosilicate-containing solid waste incineration residue to deionized water is 10:1 g / L-15:1 g / L; the leaching time is 2 h-6 h. Add the curing agent and the leachate to the second mixture, and then mix to obtain the mixture to be treated; The mixture to be treated is soaked, and then the soaked material is sequentially subjected to a first drying treatment, a molding treatment, a drying treatment and a second drying treatment to obtain the solid adsorbent; the soaking time is 24 h-48 h. The mass ratio of the siliceous porous matrix material, the calcium aluminosilicate-containing solid waste incineration residue, the adhesive, the surfactant, the curing agent, and the leachate is 40%-60%:10%-25%:2%-8%:1%-5%:5%-15%:10%-25%; The adhesive is at least one of polyacrylamide and polyvinyl alcohol; the surfactant is at least one of sodium dodecyl sulfate and hexadecyltrimethylammonium bromide; and the curing agent is at least one of cement and metakaolin.

[0006] In some embodiments, the siliceous porous matrix material is at least one of perlite and diatomaceous earth; the solid waste incineration residue containing calcium aluminosilicate is at least one of waste incineration fly ash and high-calcium fly ash.

[0007] In some embodiments, the shaped form is a spherical particle.

[0008] In some embodiments, the diameter of a single spherical particle after molding is 5-8 mm and the mass is 0.25 g ± 0.05 g.

[0009] The present invention also provides the application of a solid adsorbent prepared according to the preparation method described above in the treatment of phosphorus-containing wastewater.

[0010] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention achieves a synergistic improvement in low-cost preparation and high-efficiency phosphorus removal performance by using leachate from solid waste incineration residue as a modifier for solid adsorbents.

[0011] Other features and beneficial effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other beneficial effects of the invention can be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 The graphs show the phosphorus adsorption performance of the solid adsorbents obtained in Example 1 and Comparative Example 1. Figure 2 The graphs show the phosphorus adsorption performance of the solid adsorbents obtained in Example 1 and Comparative Example 2. Figure 3 The images show the morphology of the solid adsorbents obtained in Example 1 and Comparative Example 3, where a is Comparative Example 3 and b is Example 1. Figure 4 SEM images of the solid adsorbents obtained in Example 1 and Comparative Example 3 are shown, where a and b are from Comparative Example 3, and c and d are from Example 1. Figure 5 The images show the XRD patterns of the solid adsorbents obtained in Example 1 and Comparative Example 3, where a is Comparative Example 3 and b is Example 1. Figure 6 The graphs show the P adsorption performance of the solid adsorbents obtained in Example 1 and Comparative Example 3 under different adsorbent addition amounts, where a is Comparative Example 3 and b is Example 1. Figure 7 The graphs show the P adsorption performance of the solid adsorbents obtained in Example 1 and Comparative Example 3 at different pH values, where a is Comparative Example 3 and b is Example 1. Figure 8 The graphs show the P adsorption performance of the solid adsorbents obtained in Example 1 and Comparative Example 3 at different initial phosphorus concentrations, where a is Comparative Example 3 and b is Example 1. Figure 9 The graphs show the P adsorption performance of the solid adsorbents obtained in Example 1 and Comparative Example 3 at different adsorption times, where a represents Comparative Example 3 and b represents Example 1. Figure 10 The figures are fitting curves for the solid adsorbents obtained in Example 1 and Comparative Example 3, where a is Comparative Example 3 and b is Example 1. Figure 11 The images show the Cl 2p high-resolution XPS spectra of the solid adsorbent obtained in Example 1 before and after phosphorus adsorption and removal, where a is before phosphorus adsorption and removal, b is after phosphorus adsorption and removal, and c is a comparison image before and after phosphorus adsorption and removal. Figure 12 This is a distribution diagram of heavy metal content in wastewater before and after phosphorus removal by the solid adsorbent obtained in Example 1; Figure 13This is a distribution diagram of heavy metal content in wastewater before and after phosphorus removal by the solid adsorbent obtained in Comparative Example 3. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0015] This invention provides a method for preparing a solid adsorbent, comprising the following steps: Weigh and mix at least one siliceous porous matrix material from perlite and diatomite with at least one calcium-containing aluminosilicate solid waste incineration residue from waste incineration fly ash and high-calcium fly ash according to a preset ratio to obtain a first mixture material; Add at least one of polyacrylamide and polyvinyl alcohol as an adhesive and at least one of sodium dodecyl sulfate and hexadecyltrimethylammonium bromide as a surfactant to the first mixture, and then mix to obtain a second mixture; A leachate is provided, which is obtained by mixing and leaching the calcium aluminosilicate-containing solid waste incineration residue with deionized water at a solid-liquid ratio of 10:1 g / L to 15:1 g / L for 2 h to 6 h. Add at least one of cement, metakaolin, and the leachate to the second mixture, and then mix to obtain the mixture to be treated; The mass ratio of the siliceous porous matrix material, the calcium aluminosilicate-containing solid waste incineration residue, the adhesive, the surfactant, the curing agent and the leachate is 40%-60%:10%-25%:2%-8%:1%-5%:5%-15%:10%-25%.

[0016] The mixture to be treated is soaked for 24-48 hours, and then subjected to a first drying treatment, a molding treatment, a drying treatment, and a second drying treatment in sequence to obtain the solid adsorbent. The molded form is spherical particles, with each spherical particle having a diameter of 5-8 mm and a mass of 0.25 g ± 0.05 g.

[0017] It should be noted that the silica porous matrix material and the calcium aluminosilicate-containing solid waste incineration residue are first weighed and thoroughly mixed according to the specified ratio to ensure uniform distribution of each component. Subsequently, binders and surfactants are added to enhance particle strength and improve material dispersibility. The addition of a curing agent further improves the mechanical strength and stability of the particles, while simultaneously "locking in" heavy metals in the calcium aluminosilicate-containing solid waste incineration residue, preventing secondary pollution during wastewater treatment. The leachate is preferably added to the system along with the curing agent after the binder and surfactant have been added to form the second mixture. This avoids premature addition of the leachate, which could lead to excessively high local moisture content, agglomeration, or uneven formation of the material. The active components in the leachate, such as calcium, silicon, and aluminum, can migrate uniformly under the action of the curing agent and participate in the modification of the particle surface and pore structure, which is beneficial for improving the mechanical strength, water stability, and phosphorus removal adsorption performance of the resulting solid adsorbent. Simultaneously, the curing agent helps to solidify and stabilize heavy metals in the residue, reducing the risk of secondary pollution. Furthermore, the leaching time of the leachate and the soaking time of the mixture to be treated affect the release, migration, and solidification degree of the active components. If the leaching time or soaking time is too short, the modification will be insufficient, and the improvement in phosphorus removal performance and particle stability will be limited. If the time is too long, it may lead to excessive release of soluble impurities or loss of active components. Therefore, the leaching time is preferably 2-6 h, and the soaking time is preferably 24-48 h, in order to balance the release of active components, particle forming stability, and adsorption performance.

[0018] It should be noted that during the adsorbent preparation process, the type and particle size of the binder (such as polyacrylamide), curing agent (such as cement), and framework materials (such as perlite and diatomaceous earth) all significantly affect the performance of solid adsorbent particles. Specifically: if the ratio of binder to curing agent is inappropriate, the solid adsorbent will crack after reacting in phosphorus-containing wastewater for a period of time, easily leading to overall fragmentation; if insufficient framework materials are added, the adsorbent will be difficult to form in water, and its morphology will be no different from powdered fly ash; if the solid adsorbent particles are too large, the internal structure will become unstable, and it will easily self-disintegrate after soaking in wastewater for a period of time. Any of the above situations will cause significant structural damage to the solid adsorbent in wastewater, thereby causing secondary pollution to the wastewater.

[0019] The present invention also provides the application of a solid adsorbent prepared according to the preparation method described above in the treatment of phosphorus-containing wastewater.

[0020] Performance testing: At 25 ℃, one modified waste incineration fly ash granular adsorbent (mass 0.25 g ± 0.05 g) was added to phosphorus-containing wastewater and allowed to stand for 12 h before sampling. Based on an adsorbent dosage of 25 g / L, a temperature of 25 ℃, an initial phosphorus concentration of 15 mg / L in the wastewater, pH=7, and an adsorption time of 12 h, the effects of adsorbent dosage (10–50 g / L), solution pH (3–11), initial phosphorus concentration (10–100 mg / L), and adsorption time (5–120 min) on the phosphorus removal performance of the solid adsorbent were investigated to determine the optimal adsorption conditions. Under these optimal conditions, the phosphorus removal performance of different adsorbents was compared. Simultaneously, pseudo-first-order and pseudo-second-order kinetic models were used to fit the adsorption data. The phosphorus-containing wastewater was prepared as follows: analytical grade KH₂PO₄ was dissolved in deionized water.

[0021] Analysis method: 1) Determination of phosphorus in wastewater after adsorption The concentration of phosphorus in the solution was determined using the ammonium molybdate spectrophotometric method according to the standard GB11893-89. The formula for calculating the adsorption capacity is as follows:

[0022] Among them, Q e —Adsorption capacity, mg / g; C e —The residual phosphorus concentration in the water sample after adsorption, in mg / L; C0—Initial phosphorus concentration in the water sample, mg / L; m — Mass of modified incineration fly ash particulate adsorbent, g; V – Water sample volume, L.

[0023] 2) Detection of heavy metals in wastewater after adsorption The metal concentration in the solution after adsorption was determined using the method described in "Determination of 65 Elements in Water by Inductively Coupled Plasma Mass Spectrometry" (HJ 700—2014) and the hot plate digestion method. The formula for calculating the metal content is as follows:

[0024] in, ρ —The concentration of the element in the sample, in mg / L; ρ 1 — The concentration of the element in the diluted sample, in mg / L; ρ 2 — The mass concentration of the element in the diluted laboratory blank sample, in mg / L; f —Mass of modified incineration fly ash particulate adsorbent, in g; V – Dilution factor.

[0025] 3) Fitting the dynamic model The adsorption data were fitted using pseudo-first-order and pseudo-second-order kinetic models, and the fitting formulas are as follows: ln(q e -q t )=lnqe-k1t

[0026]

[0027] Where, q e —Equilibrium adsorption capacity, mg / g; q t —Adsorption amount at time t, mg / g; k1—rate constant of the quasi-first-order model, min - ¹; k2 — Rate constant of the pseudo-second-order model, g·mg·min - ¹; α — Initial adsorption rate; β—Elovich constant, g / mg.

[0028] The present invention will be further described in detail below with reference to specific embodiments. These embodiments will enable those skilled in the art to gain a more comprehensive understanding of the invention, but do not limit the invention in any way. Where techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0029] In the description of this invention, it should be noted that all terms used in this invention (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and should not be construed as limiting the invention; it should be further understood that the terms used in this invention should be understood to have the same meaning as those in the context of this specification and in the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this invention.

[0030] Example 1: This embodiment provides a method for preparing a solid adsorbent, including: Perlite (particle size less than 200 mesh, analytical grade, Fengfengshun Stone Powder Plant), diatomaceous earth (particle size less than 200 mesh, analytical grade, Tianjin Huasheng), waste incineration fly ash (from Xiamen Haicang Waste Incineration Plant), polyacrylamide (molecular weight 12 million, Tianjin Zhiyuan), sodium dodecyl sulfate (Tianjin Zhiyuan, needle-like), cement (Xiamen Tongan Chengchuang), and leachate in a mass ratio of 25%:25%:16%:5%:3%:10%:16%. The waste incineration fly ash (from Xiamen Haicang Waste Incineration Plant) was mixed with deionized water at a liquid-to-solid ratio of 10:1, leached for 2 hours, and filtered to obtain the fly ash leachate. The specific preparation method is as follows: First, perlite, diatomaceous earth, and incineration fly ash were weighed and thoroughly mixed according to the specified ratio. Then, polyacrylamide and sodium dodecyl sulfate were added, followed by cement and leachate. The mixture was soaked at room temperature for 24 hours and dried at 60°C until it could be formed. It was then manually extruded into spherical particles with a diameter of approximately 5 mm, with each particle weighing approximately 0.2 g to ensure the uniformity and comparability of the adsorbent. The formed particles were then allowed to air dry at room temperature for 24 hours, followed by drying at 60°C for 4 hours to obtain the final solid adsorbent.

[0031] Comparative Example 1: This comparative example provides a method for preparing a solid adsorbent. Compared with Example 1, the fly ash leachate is replaced with deionized water, while other conditions remain the same. The spherical adsorbent particles formed in this comparative example have a diameter of approximately 6 mm and a weight of approximately 0.22 g per particle.

[0032] The phosphorus adsorption performance of the solid adsorbents prepared in Example 1 and this comparative example was tested, and the results are as follows: Figure 1 As shown in the figure. Compared with Example 1, the phosphorus adsorption performance of this comparative example is significantly reduced. Example 1 exhibits a faster adsorption rate in the initial stage of adsorption, reaching approximately 1.90 mg / g of phosphorus adsorption at about 24 h and approximately 2.10 mg / g at about 36 h, and then basically stabilizing; while the phosphorus adsorption of this comparative example is lower at the same adsorption time, with an equilibrium adsorption capacity of approximately 1.26 mg / g, significantly lower than that of Example 1. The above results indicate that replacing the fly ash leachate with deionized water reduces both the phosphorus adsorption capacity and adsorption efficiency of the obtained solid adsorbent. The introduction of fly ash leachate is beneficial to improving the phosphorus removal performance of the solid adsorbent, indicating that the preparation system used in Example 1 has a better adsorption effect.

[0033] Comparative Example 2: This comparative example provides a method for preparing a solid adsorbent. Compared with Example 1, the mass ratio of perlite, diatomaceous earth, waste incineration fly ash (from Xiamen Haicang Waste Incineration Plant), polyacrylamide (molecular weight 12 million, Tianjin Zhiyuan), sodium dodecyl sulfate (Tianjin Zhiyuan), cement (Xiamen Tong'an Chengchuang), and leachate is 30%:30%:16%:5%:3%:10%:6%, with other conditions remaining the same. The spherical adsorbent particles formed in this comparative example have a diameter of approximately 5 mm and a weight of approximately 0.2 g per particle.

[0034] The phosphorus adsorption performance of the solid adsorbents prepared in Example 1 and Comparative Example 2 was tested, and the results are as follows: Figure 2 As shown, both solid adsorbents possess a certain phosphorus adsorption capacity. However, compared to Comparative Example 2, Example 1 exhibits a faster adsorption rate and a higher equilibrium adsorption capacity. In Example 1, the phosphorus adsorption capacity increases rapidly in the initial adsorption stage, reaching approximately 1.90 mg / g after about 24 hours and approximately 2.10 mg / g after about 36 hours, subsequently remaining relatively stable. In contrast, the adsorption capacity of Comparative Example 2 increases relatively slowly, with an equilibrium adsorption capacity of approximately 1.60 mg / g, significantly lower than that of Example 1. This indicates that the proportion of fly ash impregnation solution in the raw material formulation has a significant impact on the adsorption performance of the solid adsorbent, and the higher proportion of fly ash impregnation solution in Example 1 is more conducive to improving the phosphorus removal effect of the material.

[0035] Comparative Example 3: This comparative example provides a method for preparing a solid adsorbent. Compared with Example 1, the fly ash leachate is replaced with an iron solution, while other conditions remain the same. The spherical adsorbent particles formed in this comparative example have a diameter of approximately 5 mm and a weight of approximately 0.2 g per particle.

[0036] The iron solution was prepared from ferrous sulfate heptahydrate (FeSO4·7H2O, analytical grade) with a concentration of 2 mol / L.

[0037] from Figure 3 As can be seen, the solid adsorbent particles prepared by the methods used in Example 1 and Comparative Example 3 have regular shapes, are approximately spherical, and are uniform in size. Their surfaces have no obvious cracks or pores, indicating good forming effect and a relatively compact internal structure. Due to the addition of Fe ions for modification, the solid adsorbent particles prepared by soaking in iron solution are light yellow after drying, indicating that the iron ions are still uniformly distributed inside the particles. During the drying process, the iron ions inside the particles undergo further oxidation, and some crystals precipitate, but the color change is not significant. In contrast, the solid adsorbent particles prepared by soaking in fly ash leachate are generally grayish-white with a relatively smooth surface.

[0038] Analysis using scanning electron microscopy (SEM, ZEISS SIGMA) and X-ray diffraction (XRD, Ultima IVPhaser) revealed significant differences in the microstructure and phase composition of the adsorbents obtained in Example 1 and Comparative Example 3. Figure 4 , Figure 5 The solid adsorbent obtained by immersion in iron solution exhibits a relatively disordered structure with numerous fine particles and irregular aggregates adhering to its surface, indicating uneven distribution of active components and potential local agglomeration and pore obstruction. In contrast, the solid adsorbent obtained by immersion in fly ash leachate presents a more complete lamellar structure with a relatively regular surface and fewer adhering impurity particles, indicating a more uniform distribution of surface mineral phases and a more stable structure. This more ordered surface morphology is beneficial for exposing active sites and reducing mass transfer resistance, thereby enhancing the contact and binding of phosphate with the material surface. XRD results show that both solid adsorbents are dominated by mineral phases such as CaCO3, CaSO4, and SiO2, indicating that typical calcium-based and silicon-based inorganic components are retained in the materials. Among them, CaCO3 and CaSO4 can provide calcium sources for phosphate removal and promote phosphate fixation on the material surface. In contrast, the solid adsorbent obtained by immersion in fly ash leachate exhibits clearer diffraction peaks and fewer impurity peaks, indicating a more concentrated crystalline phase composition and more obvious crystallization characteristics, suggesting a more stable and ordered surface mineral structure. The SEM results show that the solid adsorbent obtained by soaking in fly ash leachate forms a relatively regular plate-like crystal structure, indicating that its surface active components are more evenly distributed.

[0039] The effects of adsorbent dosage, pH, initial phosphorus concentration, and adsorption time on the solid adsorbent obtained by leaching fly ash in leachate and the solid adsorbent obtained by leaching iron solution showed similar overall trends, but differences existed in adsorption capacity, rate, and stability. Under the influence of adsorbent dosage, the solid adsorbent obtained by leaching fly ash in leachate also reached its optimal adsorption capacity of 0.58 mg / g at approximately 3 g / L, but under the same dosage conditions, its unit adsorption capacity was lower than that of the solid adsorbent obtained by leaching iron solution (0.64 mg / g). Figure 6 This may be due to the increased stacking and agglomeration of particles, which further reduces site utilization and decreases the adsorption capacity per unit. As the dosage continues to increase, the adsorption capacity per unit gradually decreases. This pattern is basically consistent for both types of solid adsorbents, indicating that both types of fly ash particulate adsorbents are affected by both site utilization and the unit mass distribution effect under changes in dosage.

[0040] Regarding pH, the solid adsorbent obtained by soaking in fly ash leachate showed relatively better adsorption performance under weakly alkaline conditions, reaching a peak adsorption capacity of 1.66 mg / g at pH=12, which is higher than that of the solid adsorbent obtained by soaking in iron solution (pH=10, 1.40 mg / g). This indicates that this method is more conducive to the formation of a surface active phase suitable for phosphorus fixation. This is because the soluble inorganic active components such as Ca and Al in the fly ash leachate are redistributed on the particle surface during the modification process, or promote surface mineral phase reconstruction, thereby enhancing the surface complexation, precipitation, and synergistic fixation effect between the material and phosphate ions under alkaline conditions. However, the curve fluctuations become larger, indicating greater sensitivity to acidic and alkaline environments. Figure 7 The reason is that the solid adsorbent obtained by soaking fly ash in leachate relies solely on the calcium, silicon, aluminum and other mineral components of fly ash itself to play its role. It lacks stable binding sites provided by iron-based hydroxyl oxides, and its surface charge and structure are easily affected by pH, resulting in a large fluctuation in adsorption capacity.

[0041] The adsorption capacity of the solid adsorbent obtained by leaching fly ash in leachate showed a similar trend to that of the solid adsorbent obtained by leaching in iron solution, but the adsorption capacity was higher. The maximum adsorption capacity was reached at an initial phosphorus concentration of 20 mg / L. Specifically, the adsorption capacity of the solid adsorbent obtained by leaching fly ash in leachate was 0.72 mg / g, while that obtained by leaching in iron solution was 0.58 mg / g. Figure 8 As the concentration continued to increase, the adsorption capacity decreased slightly, but remained at a high level overall. This indicates that the solid adsorbent obtained from fly ash leachate still possesses good active site utilization and strong phosphorus fixation potential under high phosphorus loading conditions, and may have better adaptability to situations with large concentration fluctuations in actual phosphorus-containing wastewater. It is noteworthy that the solid adsorbent obtained from fly ash leachate reached a final equilibrium adsorption capacity of approximately 2.10 mg / g after 30 hours. Figure 9 The concentration of fly ash leachate was higher than that of solid adsorbent obtained by immersion in iron solution (1.92 mg / g), indicating that fly ash leachate is more conducive to improving the overall adsorption capacity of the material.

[0042] Adsorption kinetics results show that ( Figure 10 The solid adsorbent obtained by soaking in fly ash leachate exhibits a rapid adsorption followed by a slow equilibrium. Tables 1 and 2 show that the fitting curves of each model generally agree well with the experimental data, with the pseudo-first-order kinetic model showing the highest goodness of fit. This indicates that the removal of phosphorus by this material is also controlled by both surface site occupancy and mass transfer diffusion processes. Meanwhile, the adsorption process of the solid adsorbent obtained by soaking in fly ash leachate shows a better fit (with a higher R-value). 2The value indicates that its adsorption behavior is more stable. In addition, its pseudo-first-order rate constant k1 and the initial adsorption rate parameter α of the Elovich model are both slightly higher than those of the solid adsorbent obtained by soaking in iron solution, indicating that the solid adsorbent obtained by soaking in fly ash leachate has a faster initial adsorption rate and stronger surface reactivity.

[0043] Table 1. Kinetic fitting parameters for phosphorus adsorption by solid adsorbents obtained from iron solution immersion.

[0044] Table 2. Kinetic fitting parameters for phosphorus adsorption by solid adsorbents obtained from fly ash leachate leaching.

[0045] In summary, based on adsorption capacity, the solid adsorbent obtained by soaking in fly ash leachate exhibits a higher equilibrium adsorption capacity. According to the kinetic fitting results, the solid adsorbent obtained by soaking in fly ash leachate in the pseudo-first-order kinetic model has a higher q... e The concentration was 2.15 mg / g, higher than the 2.01 mg / g of the solid adsorbent obtained by immersion in iron solution; in the pseudo-second-order kinetic model, its q e The adsorption capacity was 2.66 mg / g, which is also higher than the 2.54 mg / g of the solid adsorbent obtained by leaching in iron solution. As can be seen from the adsorption time curve, the final experimental equilibrium adsorption capacity of the solid adsorbent obtained by leaching in fly ash leachate is also higher than that of the solid adsorbent obtained by leaching in iron solution, indicating that it can provide more effective reaction sites or has a stronger phosphorus fixation effect under the same conditions.

[0046] From the perspective of adaptability to operating conditions, the solid adsorbent obtained by leaching fly ash in leachate shows a more significant advantage under alkaline conditions and higher initial phosphorus concentrations. Figure 7 It can be seen that the adsorption capacity of both materials increases with increasing pH, but the solid adsorbent obtained by soaking in fly ash leachate shows a greater increase under high pH conditions, with a significantly higher maximum adsorption capacity than the solid adsorbent obtained by soaking in iron solution. Figure 8 It can be seen that within the range of medium to high initial phosphorus concentrations, the solid adsorbent obtained by leaching in fly ash leachate maintained a higher adsorption capacity, while the solid adsorbent obtained by leaching in iron solution showed a more significant decrease, indicating that the former has a stronger ability to adapt to high loads. This result suggests that the solid adsorbent obtained by leaching in fly ash leachate is more beneficial for improving the operational stability and application potential of materials under complex water quality conditions.

[0047] From the perspective of adsorption mechanism, iron solution immersion can introduce iron-containing active sites on the material surface, thereby enhancing its interaction with phosphate. However, during particle formation, some iron species may be embedded inside the particles or unevenly distributed, resulting in a limited number of effective sites actually exposed. Simultaneously, iron solution immersion also covers, to some extent, the Ca- and Al-based active components in the original fly ash that are beneficial for phosphorus removal, thus weakening the material's original synergistic phosphorus removal ability. In contrast, fly ash leachate immersion tends to utilize the soluble inorganic active components of the fly ash system itself, enhancing the active sites on the particle surface through surface reloading and mineral phase reconstruction, promoting surface complexation, precipitation fixation, and multi-mechanism synergistic removal of phosphate, thus resulting in superior overall phosphorus removal performance. Furthermore, the XPS full spectrum of the solid adsorbent obtained from fly ash leachate immersion before and after phosphorus adsorption shows (…). Figure 11 Compared to before adsorption, the relative content of Cl element after phosphorus removal decreased significantly, indicating that phosphate ions may have replaced chloride ions on the adsorbent surface through ion exchange. This is one of the important mechanisms for phosphorus removal by solid adsorbents obtained from fly ash leachate leaching. Compared with solid adsorbents obtained from iron solution leaching, solid adsorbents obtained from fly ash leachate leaching have stronger ion exchange capacity, thus resulting in higher overall phosphorus removal efficiency.

[0048] From a cost perspective, the two methods for obtaining solid adsorbents differ significantly in terms of raw material input and process complexity. Solid adsorbents obtained by leaching fly ash in leachate do not require the addition of external chemical reagents such as metal salts during preparation. Instead, they utilize the soluble active components in the fly ash leachate itself to modify the material. Therefore, the preparation route is simpler, the raw material utilization rate is higher, and the economic investment from added reagents is reduced. This modification method fully utilizes the active components such as Ca and Al within the fly ash system, embodying the characteristics of "waste treatment" and endogenous recycling, while also reducing reagent consumption and potential secondary pollution risks during the process. Therefore, it has significant advantages in terms of material preparation cost and resource utilization. In contrast, solid adsorbents obtained by leaching iron solution require the addition of iron-containing reagents during preparation to construct Fe-dominated active sites, thereby enhancing the material's binding capacity to phosphate. Although this method can improve the surface reactivity of the material by introducing external iron components, its process is relatively more complex, and the reagent cost, addition control requirements, and subsequent operation costs are correspondingly increased. Therefore, from the perspective of economy and process simplicity, the preparation cost of iron solution leaching is generally higher than that of fly ash leachate leaching. This indicates that fly ash leachate leaching has the dual advantages of low-cost preparation and superior phosphorus removal performance, better meeting the need for synergistic improvement of economic efficiency and functionality in the utilization of fly ash resources. Therefore, from the perspective of practical engineering application and large-scale promotion, solid adsorbents obtained by fly ash leachate leaching are more advantageous in terms of economic feasibility and application potential.

[0049] Furthermore, a comparison was made of the precipitation of heavy metals in phosphorus-containing wastewater before and after adsorption by the solid adsorbent obtained from leaching fly ash in fly ash leachate. Figure 12 The results showed that the amount of heavy metals precipitated after adsorption was within the normal range. The concentration of the metal precipitates after adsorption all met the Class I standard of the "Integrated Industrial Wastewater Discharge Standard" (GB 8978-1996). On the other hand, the heavy metal precipitation of fly ash soaked in Fe solution before and after adsorption was compared. Figure 13 The results showed that the amount of heavy metals leached after adsorption was also within the normal range. These results confirm that the obtained solid adsorbent is harmless to the environment and has the potential for large-scale application in waste incineration plants.

[0050] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for producing a solid adsorbent, characterized by, Includes the following steps: At least one siliceous porous matrix material and calcium aluminosilicate solid waste incineration residue are weighed and mixed according to a preset ratio to obtain a first mixture. A binder and a surfactant are added to the first mixture, and the mixture is then mixed to obtain a second mixture. A leachate is provided, which is obtained by mixing and leaching the calcium aluminosilicate-containing solid waste incineration residue with deionized water; in the process of obtaining the leachate, the solid-liquid ratio of the calcium aluminosilicate-containing solid waste incineration residue to deionized water is 10:1 g / L-15:1 g / L; the leaching time is 2 h-6 h. Add the curing agent and the leachate to the second mixture, and then mix to obtain the mixture to be treated; The mixture to be treated is soaked, and then the soaked material is sequentially subjected to a first drying treatment, a molding treatment, a drying treatment and a second drying treatment to obtain the solid adsorbent; the soaking time is 24 h-48 h. The mass ratio of the siliceous porous matrix material, the calcium aluminosilicate-containing solid waste incineration residue, the adhesive, the surfactant, the curing agent, and the leachate is 40%-60%:10%-25%:2%-8%:1%-5%:5%-15%:10%-25%; The adhesive is at least one of polyacrylamide and polyvinyl alcohol; the surfactant is at least one of sodium dodecyl sulfate and hexadecyltrimethylammonium bromide; and the curing agent is at least one of cement and metakaolin.

2. The production method according to claim 1, characterized by, The siliceous porous matrix material is at least one of perlite and diatomaceous earth; the solid waste incineration residue containing calcium aluminosilicate is at least one of waste incineration fly ash and high-calcium fly ash.

3. The preparation method according to claim 1, characterized in that, The formed shape is a spherical particle.

4. The method of claim 1, wherein, The diameter of each spherical particle after molding is 5-8 mm, and its mass is 0.25 g ± 0.05 g.

5. The application of a solid adsorbent prepared by the preparation method according to any one of claims 1-4 in the treatment of phosphorus-containing wastewater.

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